<template>
  <div>
    <van-uploader :after-read="onRead" accept="image/*" :max-count="1">
      <slot></slot>
    </van-uploader>
  </div>
</template>

<script>
import Exif from 'exif-js'
export default {
  data() {
    return {
      files: {},
      picValue: ''
    }
  },
  methods: {
    // afterRead(file) {
    //   this.$emit('afterRead', file)
    // },
    // 组件方法 获取 流
    async onRead(file) {
      
      this.$toast.loading({
        duration: 60000, // 持续展示 toast
        forbidClick: true,
        message: '上传中~'
      })
      console.log('file.file.size',file.file.size)
      console.log('file.file--------------',file.file);
      if (file.file.size>1024*1024*8) {
        this.$toast('照片过大,请上传小于8M的照片')
        return
      }
      // console.log(file)
      
      this.$emit('afterRead', file.file)
      //this.files.name = file.file.name // 获取文件名
      //this.files.type = file.file.type // 获取类型
      //this.picValue = file.file // 文件流
      //this.imgPreview(this.picValue)
    },
    // 处理图片
    imgPreview(file) {
      let self = this
      let Orientation
      //去获取拍照时的信息，解决拍出来的照片旋转问题
      Exif.getData(file, function() {
        Orientation = Exif.getTag(this, 'Orientation')
      })
      // 看支持不支持FileReader
      //if (!file || !window.FileReader) return
      if (!file || !window.FileReader){
        console.log('不支持FileReader--------')
        self.headerImage = file
        postImg()
      }else{
        console.log('支持FileReader')
        console.log('当前是否为图片类型',/^image/.test(file.type))
        console.log('img的type类型是------',file.type)
        if (/^image/.test(file.type)) {
          // 创建一个reader
          let reader = new FileReader()
          // 将图片2将转成 base64 格式
          reader.readAsDataURL(file)
          // 读取成功后的回调
          reader.onloadend = function() {
            console.log('this.result--读取成功-');
            let result = this.result
            let img = new Image()
            img.src = result
            //判断图片是否大于500K,是就直接上传，反之压缩图片
            if (this.result.length <= 500 * 1024) {
              console.log('不大于500k')
              self.headerImage = this.result
              self.postImg()
            } else {
              img.onload = function() {
                console.log('大于500k')
                let data = self.compress(img, Orientation)
                self.headerImage = data
                self.postImg()
              }
            }
          }
        }else{
          this.$toast.fail({
            duration: 5000, // 持续展示 toast
            forbidClick: true,
            message: '该照片格式读取失败，请换张照片重新上传'
          })
        }
      }
    },
    // 压缩图片
    compress(img, Orientation) {
      let canvas = document.createElement('canvas')
      let ctx = canvas.getContext('2d')
      //瓦片canvas
      let tCanvas = document.createElement('canvas')
      let tctx = tCanvas.getContext('2d')
      // let initSize = img.src.length;
      let width = img.width
      let height = img.height
      //如果图片大于四百万像素，计算压缩比并将大小压至400万以下
      let ratio
      if ((ratio = (width * height) / 4000000) > 1) {
        // console.log("大于400万像素");
        ratio = Math.sqrt(ratio)
        width /= ratio
        height /= ratio
      } else {
        ratio = 1
      }
      canvas.width = width
      canvas.height = height
      //    铺底色
      ctx.fillStyle = '#fff'
      ctx.fillRect(0, 0, canvas.width, canvas.height)
      //如果图片像素大于100万则使用瓦片绘制
      let count
      if ((count = (width * height) / 1000000) > 1) {
        // console.log("超过100W像素");
        count = ~~(Math.sqrt(count) + 1) //计算要分成多少块瓦片
        //      计算每块瓦片的宽和高
        let nw = ~~(width / count)
        let nh = ~~(height / count)
        tCanvas.width = nw
        tCanvas.height = nh
        for (let i = 0; i < count; i++) {
          for (let j = 0; j < count; j++) {
            tctx.drawImage(
              img,
              i * nw * ratio,
              j * nh * ratio,
              nw * ratio,
              nh * ratio,
              0,
              0,
              nw,
              nh
            )
            ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh)
          }
        }
      } else {
        ctx.drawImage(img, 0, 0, width, height)
      }
      //修复ios上传图片的时候 被旋转的问题
      if (Orientation != '' && Orientation != 1) {
        switch (Orientation) {
          case 6: //需要顺时针（向左）90度旋转
            this.rotateImg(img, 'left', canvas)
            break
          case 8: //需要逆时针（向右）90度旋转
            this.rotateImg(img, 'right', canvas)
            break
          case 3: //需要180度旋转
            this.rotateImg(img, 'right', canvas) //转两次
            this.rotateImg(img, 'right', canvas)
            break
        }
      }
      //进行最小压缩
      let ndata = canvas.toDataURL('image/jpeg', 0.1)
      tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0
      return ndata
    },
    // 旋转图片
    rotateImg(img, direction, canvas) {
      //最小与最大旋转方向，图片旋转4次后回到原方向
      const min_step = 0
      const max_step = 3
      if (img == null) return
      //img的高度和宽度不能在img元素隐藏后获取，否则会出错
      let height = img.height
      let width = img.width
      let step = 2
      if (step == null) {
        step = min_step
      }
      if (direction == 'right') {
        step++
        //旋转到原位置，即超过最大值
        step > max_step && (step = min_step)
      } else {
        step--
        step < min_step && (step = max_step)
      }
      //旋转角度以弧度值为参数
      let degree = (step * 90 * Math.PI) / 180
      let ctx = canvas.getContext('2d')
      switch (step) {
        case 0:
          canvas.width = width
          canvas.height = height
          ctx.drawImage(img, 0, 0)
          break
        case 1:
          canvas.width = height
          canvas.height = width
          ctx.rotate(degree)
          ctx.drawImage(img, 0, -height)
          break
        case 2:
          canvas.width = width
          canvas.height = height
          ctx.rotate(degree)
          ctx.drawImage(img, -width, -height)
          break
        case 3:
          canvas.width = height
          canvas.height = width
          ctx.rotate(degree)
          ctx.drawImage(img, -width, 0)
          break
      }
    },
    //将base64转换为文件
    dataURLtoFile(dataurl) {
      var arr = dataurl.split(','),
        bstr = atob(arr[1]),
        n = bstr.length,
        u8arr = new Uint8Array(n)
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n)
      }
      return new File([u8arr], this.files.name, {
        type: this.files.type
      })
    },
    //这里写接口
    async postImg() {
      //console.log('file转换前---------',this.headerImage)

      let file = this.dataURLtoFile(this.headerImage)
      //console.log('file转换后---------',file)
      // let formData = new window.FormData()
      // formData.append('file', file)

      this.$emit('afterRead', file)
    }
  }
}
</script>

<style>
</style>